This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. The goal of this project is to detemine physiological and pyschological correlates of the decline in physical activity in African American and Latina girls during puberty. The mechanism explaining the well known decline in physical activity that occurs in girls during adolescence is not well understood and hinders the ability to establish effective health promotion interventions during this critical period. However, the fact that this phenomenon has been found consistently across gender, ethnicity and nationality in human studies, and across species in animal studies, suggests it may have a biological basis. The pubertal transtion in African American and Latina girls represents a "critical period" of development in which increased insulin resistance and decreased physical activity have been noted. These "risky" metabolic and behavioral changes in these susceptible groups may explain, in part, their increased risk for obesity, type 2 diabetes and the metabolic syndrome. 100 girls (50 Latina and 50 African American) girls will be followed from Tanner Stage 1 - Tanner Stage 3+. The research will include yearly overnight visits to the GRCR and quarterly accelerometry and questionnaire studies. The overall hypotheses of this study are that pubertal insulin resistance is linked to (downstream) metabolic and affective determinants of physical activity including mood and enery levels, and that these metabolic and psychological changes contribute to the marked decline in physical activity that occurs during puberty.